/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)

  Stockfish is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "uci.h"

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <iostream>
#include <memory>
#include <optional>
#include <sstream>
#include <string>
#include <vector>

#include "benchmark.h"
#include "evaluate.h"
#include "misc.h"
#include "movegen.h"
#include "nnue/evaluate_nnue.h"
#include "position.h"
#include "search.h"
#include "thread.h"

namespace Stockfish {

namespace {

// FEN string for the initial position in standard xiangqi
const char* StartFEN = "rnbakabnr/9/1c5c1/p1p1p1p1p/9/9/P1P1P1P1P/1C5C1/9/RNBAKABNR w";


// Called when the engine receives the "position" UCI command.
// It sets up the position that is described in the given FEN string ("fen") or
// the initial position ("startpos") and then makes the moves given in the following
// move list ("moves").
void position(Position& pos, std::istringstream& is, StateListPtr& states) {

    Move        m;
    std::string token, fen;

    is >> token;

    if (token == "startpos")
    {
        fen = StartFEN;
        is >> token;  // Consume the "moves" token, if any
    }
    else if (token == "fen")
        while (is >> token && token != "moves")
            fen += token + " ";
    else
        return;

    states = StateListPtr(new std::deque<StateInfo>(1));  // Drop the old state and create a new one
    pos.set(fen, &states->back(), Threads.main());

    // Parse the move list, if any
    while (is >> token && (m = UCI::to_move(pos, token)) != MOVE_NONE)
    {
        states->emplace_back();
        pos.do_move(m, states->back());
    }
}

// Prints the evaluation of the current position, consistent with
// the UCI options set so far.
void trace_eval(Position& pos) {

    StateListPtr states(new std::deque<StateInfo>(1));
    Position     p;
    p.set(pos.fen(), &states->back(), Threads.main());

    Eval::NNUE::verify();

    sync_cout << "\n" << Eval::trace(p) << sync_endl;
}


// Called when the engine receives the "setoption" UCI command.
// The function updates the UCI option ("name") to the given value ("value").
void setoption(std::istringstream& is) {

    Threads.main()->wait_for_search_finished();

    std::string token, name, value;

    is >> token;  // Consume the "name" token

    // Read the option name (can contain spaces)
    while (is >> token && token != "value")
        name += (name.empty() ? "" : " ") + token;

    // Read the option value (can contain spaces)
    while (is >> token)
        value += (value.empty() ? "" : " ") + token;

    if (Options.count(name))
        Options[name] = value;
    else
        sync_cout << "No such option: " << name << sync_endl;
}


// Called when the engine receives the "go" UCI command. The function
// sets the thinking time and other parameters from the input string, then starts
// with a search.
void go(Position& pos, std::istringstream& is, StateListPtr& states) {

    Search::LimitsType limits;
    std::string        token;
    bool               ponderMode = false;

    limits.startTime = now();  // The search starts as early as possible

    while (is >> token)
        if (token == "searchmoves")  // Needs to be the last command on the line
            while (is >> token)
                limits.searchmoves.push_back(UCI::to_move(pos, token));

        else if (token == "wtime")
            is >> limits.time[WHITE];
        else if (token == "btime")
            is >> limits.time[BLACK];
        else if (token == "winc")
            is >> limits.inc[WHITE];
        else if (token == "binc")
            is >> limits.inc[BLACK];
        else if (token == "movestogo")
            is >> limits.movestogo;
        else if (token == "depth")
            is >> limits.depth;
        else if (token == "nodes")
            is >> limits.nodes;
        else if (token == "movetime")
            is >> limits.movetime;
        else if (token == "mate")
            is >> limits.mate;
        else if (token == "perft")
            is >> limits.perft;
        else if (token == "infinite")
            limits.infinite = 1;
        else if (token == "ponder")
            ponderMode = true;

    Threads.start_thinking(pos, states, limits, ponderMode);
}


// Called when the engine receives the "bench" command.
// First, a list of UCI commands is set up according to the bench
// parameters, then it is run one by one, printing a summary at the end.
void bench(Position& pos, std::istream& args, StateListPtr& states) {

    std::string token;
    uint64_t    num, nodes = 0, cnt = 1;

    std::vector<std::string> list = setup_bench(pos, args);

    num = count_if(list.begin(), list.end(),
                   [](const std::string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });

    TimePoint elapsed = now();

    for (const auto& cmd : list)
    {
        std::istringstream is(cmd);
        is >> std::skipws >> token;

        if (token == "go" || token == "eval")
        {
            std::cerr << "\nPosition: " << cnt++ << '/' << num << " (" << pos.fen() << ")"
                      << std::endl;
            if (token == "go")
            {
                go(pos, is, states);
                Threads.main()->wait_for_search_finished();
                nodes += Threads.nodes_searched();
            }
            else
                trace_eval(pos);
        }
        else if (token == "setoption")
            setoption(is);
        else if (token == "position")
            position(pos, is, states);
        else if (token == "ucinewgame")
        {
            Search::clear();
            elapsed = now();
        }  // Search::clear() may take a while
    }

    elapsed = now() - elapsed + 1;  // Ensure positivity to avoid a 'divide by zero'

    dbg_print();

    std::cerr << "\n==========================="
              << "\nTotal time (ms) : " << elapsed << "\nNodes searched  : " << nodes
              << "\nNodes/second    : " << 1000 * nodes / elapsed << std::endl;
}

// The win rate model returns the probability of winning (in per mille units) given an
// eval and a game ply. It fits the LTC fishtest statistics rather accurately.
int win_rate_model(Value v, int ply) {

    // The model only captures up to 240 plies, so limit the input and then rescale
    double m = std::min(240, ply) / 64.0;

    // The coefficients of a third-order polynomial fit is based on the fishtest data
    // for two parameters that need to transform eval to the argument of a logistic
    // function.
    constexpr double as[] = {7.42211754, -26.5119614, 46.99271939, 340.67524114};
    constexpr double bs[] = {-0.50136481, 4.9383151, -11.86324223, 89.56581513};

    // Enforce that NormalizeToPawnValue corresponds to a 50% win rate at ply 64
    static_assert(UCI::NormalizeToPawnValue == int(as[0] + as[1] + as[2] + as[3]));

    double a = (((as[0] * m + as[1]) * m + as[2]) * m) + as[3];
    double b = (((bs[0] * m + bs[1]) * m + bs[2]) * m) + bs[3];

    // Transform the eval to centipawns with limited range
    double x = std::clamp(double(v), -4000.0, 4000.0);

    // Return the win rate in per mille units, rounded to the nearest integer
    return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
}

}  // namespace


// Waits for a command from the stdin, parses it, and then calls the appropriate
// function. It also intercepts an end-of-file (EOF) indication from the stdin to ensure a
// graceful exit if the GUI dies unexpectedly. When called with some command-line arguments,
// like running 'bench', the function returns immediately after the command is executed.
// In addition to the UCI ones, some additional debug commands are also supported.
void UCI::loop(int argc, char* argv[]) {

    Position     pos;
    std::string  token, cmd;
    StateListPtr states(new std::deque<StateInfo>(1));

    pos.set(StartFEN, &states->back(), Threads.main());

    for (int i = 1; i < argc; ++i)
        cmd += std::string(argv[i]) + " ";

    do
    {
        if (argc == 1
            && !getline(std::cin, cmd))  // Wait for an input or an end-of-file (EOF) indication
            cmd = "quit";

        std::istringstream is(cmd);

        token.clear();  // Avoid a stale if getline() returns nothing or a blank line
        is >> std::skipws >> token;

        if (token == "quit" || token == "stop")
            Threads.stop = true;

        // The GUI sends 'ponderhit' to tell that the user has played the expected move.
        // So, 'ponderhit' is sent if pondering was done on the same move that the user
        // has played. The search should continue, but should also switch from pondering
        // to the normal search.
        else if (token == "ponderhit")
            Threads.main()->ponder = false;  // Switch to the normal search

        else if (token == "uci")
            sync_cout << "id name " << engine_info(true) << "\n"
                      << Options << "\nuciok" << sync_endl;

        else if (token == "setoption")
            setoption(is);
        else if (token == "go")
            go(pos, is, states);
        else if (token == "position")
            position(pos, is, states);
        else if (token == "fen" || token == "startpos")
            is.seekg(0), position(pos, is, states);
        else if (token == "ucinewgame")
            Search::clear();
        else if (token == "isready")
            sync_cout << "readyok" << sync_endl;

        // Add custom non-UCI commands, mainly for debugging purposes.
        // These commands must not be used during a search!
        else if (token == "flip")
            pos.flip();
        else if (token == "bench")
            bench(pos, is, states);
        else if (token == "d")
            sync_cout << pos << sync_endl;
        else if (token == "eval")
            trace_eval(pos);
        else if (token == "compiler")
            sync_cout << compiler_info() << sync_endl;
        else if (token == "export_net")
        {
            std::optional<std::string> filename;
            std::string                f;
            if (is >> std::skipws >> f)
                filename = f;
            Eval::NNUE::save_eval(filename);
        }
        else if (token == "--help" || token == "help" || token == "--license" || token == "license")
            sync_cout
              << "\nPikafish is a powerful xiangqi engine for playing and analyzing."
                 "\nIt is released as free software licensed under the GNU GPLv3 License."
                 "\nPikafish is normally used with a graphical user interface (GUI) and implements"
                 "\nthe Universal Chess Interface (UCI) protocol to communicate with a GUI, an API, etc."
                 "\nFor any further information, visit https://github.com/official-pikafish/Pikafish#readme"
                 "\nor read the corresponding README.md and Copying.txt files distributed along with this program.\n"
              << sync_endl;
        else if (!token.empty() && token[0] != '#')
            sync_cout << "Unknown command: '" << cmd << "'. Type help for more information."
                      << sync_endl;

    } while (token != "quit" && argc == 1);  // The command-line arguments are one-shot
}


// Turns a Value to an integer centipawn number,
// without treatment of mate and similar special scores.
int UCI::to_cp(Value v) { return 100 * v / UCI::NormalizeToPawnValue; }

// Converts a Value to a string by adhering to the UCI protocol specification:
//
// cp <x>    The score from the engine's point of view in centipawns.
// mate <y>  Mate in 'y' moves (not plies). If the engine is getting mated,
//           uses negative values for 'y'.
std::string UCI::value(Value v) {

    assert(-VALUE_INFINITE < v && v < VALUE_INFINITE);

    std::stringstream ss;

    if (abs(v) < VALUE_MATE_IN_MAX_PLY)
        ss << "cp " << UCI::to_cp(v);
    else
        ss << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;

    return ss.str();
}


// Reports the win-draw-loss (WDL) statistics given an evaluation
// and a game ply based on the data gathered for fishtest LTC games.
std::string UCI::wdl(Value v, int ply) {

    std::stringstream ss;

    int wdl_w = win_rate_model(v, ply);
    int wdl_l = win_rate_model(-v, ply);
    int wdl_d = 1000 - wdl_w - wdl_l;
    ss << " wdl " << wdl_w << " " << wdl_d << " " << wdl_l;

    return ss.str();
}


// Converts a Square to a string in algebraic notation (g1, a7, etc.)
std::string UCI::square(Square s) {
    return std::string{char('a' + file_of(s)), char('0' + rank_of(s))};
}


// Converts a Move to a string in coordinate notation (g1f3, a7a8).
std::string UCI::move(Move m) {

    if (m == MOVE_NONE)
        return "(none)";

    if (m == MOVE_NULL)
        return "0000";

    Square from = from_sq(m);
    Square to   = to_sq(m);

    std::string move = UCI::square(from) + UCI::square(to);

    return move;
}


// Converts a string representing a move in coordinate notation
// (g1f3, a7a8) to the corresponding legal Move, if any.
Move UCI::to_move(const Position& pos, std::string& str) {

    for (const auto& m : MoveList<LEGAL>(pos))
        if (str == UCI::move(m))
            return m;

    return MOVE_NONE;
}

}  // namespace Stockfish
